Bare Knuckle Pickups Forum

Forum Ringside => Tech => Topic started by: Tricalibur on March 02, 2009, 12:14:33 AM

Title: Preamp Valves - matched?
Post by: Tricalibur on March 02, 2009, 12:14:33 AM

So I own two vintage Mullard 12AX7's which I believe are a matched set. I want to put them into my Matamp head but I need to buy one more to complete the preamp stage. Do preamp tubes need to be a matched set to sound the best, and do I have to drain the voltage out of the amp before I remove the old tubes?

Title: Re: Preamp Valves - matched?
Post by: martinw on March 02, 2009, 12:30:53 AM

No, and No. Just turn the amp off.

Title: Re: Preamp Valves - matched?
Post by: AdamB on March 02, 2009, 05:59:22 AM

Only the power amp valves you need to have matched to get the best out of them. Pre amp valves, you can mix and match, low gain, high gain, whatever you like :D

Title: Re: Preamp Valves - matched?
Post by: JamesHealey on March 02, 2009, 11:26:08 PM

yea pre-amp tubes are cathode biased which means it doesn't matter you can just about drop anything in there and it'll work, yet ideally in a perfect world u'd change the anode resistor and cathode resistor for new types of pre-amp tube like 12AU7 to get the perfect bias.. but who the hell does that?

Just plug and play my friend.

Title: Re: Preamp Valves - matched?
Post by: the_bleeding on March 14, 2009, 08:12:48 PM

since preamp tubes amplify by cascading each stage sequentially, matched bias doesnt matter.

Matched bias only matters in the output section of Push/pull amps, because it splits your signal in 2, and amplifies the negative and positive sides seperately, and you want those sides amplified equally.